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CELL REPRODUCTION. THE CELL CYCLE AND MITOSIS. Lesson Objectives—Cell Cycle. Describe the properties of cell division in prokaryotes.

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Cell reproduction




Lesson objectives cell cycle
Lesson Objectives—Cell Cycle

  • Describe the properties of cell division in prokaryotes.

  • Describe cell division in eukaryotes. Explain the main differences between cell division in prokaryotic and eukaryotic cells.

  • Describe the basic properties of chromosomes.

  • Describe the key steps in the cell cycle.

  • Identify and describe the main processes in mitosis.

  • Describe how the cell cycle is controlled and define cancer.

Cell reproduction1

  • Cell Division: process by which a cell divides to form two new cells (daughter cells)

  • Three types of cell division, or cell reproduction

    • Prokaryotes (bacteria)

      • Binary fission divides forming two new identical cells

    • Eukaryotes

      • Mitosis

        • Cell or organism growth

        • Replacement or repair of damaged cells

      • Meiosis

        • formation of sex cells, or gametes

Why do cells divide
Why do cells divide?

1: DNA Overload

  • If cells grow without limit, an “information crisis” would develop

  • DNA cannot serve the needs of the increasing size of cell

    2: Exchange of materials

  • Food and oxygen have to cross membrane very quickly

  • Waste must get out

  • If cell is too large, this occurs too slowly and cell will die

Prokaryotic cell division

  • Binary fission

    • 3 main steps:

      1: DNA Replication—DNA is copied, resulting in 2

      identical chromosomes

      2: Chromosome Segregation—2 chromosomes separate,

      move towards ends (poles) of cell

      3: Cytokinesis—cytoplasm divides, forming 2 cells

    • Each new daughter cell is

      genetically identical to parent cell

The cell cycle

G1 phase

M phase

S phase

G2 phase

Cell cycle interphase

  • Interphase: period of growth and DNA replication between cell divisions

  • Three phases:

    • G1 Phase

      • cell increases in size

    • S Phase

      • Replication of chromosomes

        • Now two strands called sister chromatids joined by a centromere

    • G2 Phase

      • organelles double

      • new cytoplasm forms

      • All other structures needed for mitosis form

Eukaryotic cell division

  • DNA found on chromosomes located in nucleus of cell

  • Cell cycle continuous process

    • Cells grow

    • DNA replicated

    • Organelles duplicated

    • Divide to form daughter cells

    • 2 Main steps:

      1: Mitosis (4 steps—Prophase, Metaphase, Anaphase, Telophase)

      Nucleus divides

      2: Cytokinesis—Cytoplasm divide, forming 2 cells

      Each new daughter cell is genetically identical to parent cell

  • Mitosis = nuclear division

  • Mitosis is followed by cytokinesis (cell division)

  • The steps of mitosis ensure that each new cell has the exact same number of chromosomes as the original


  • Process that divides cell nucleus to produce two new nuclei each with a complete set of chromosomes

  • Continuous process

  • Four phases (PMAT)

    • Prophase

    • Metaphase

    • Anaphase

    • Telophase

  • (1)Prophase

  • (2)Metaphase

  • (3)Anaphase

  • (4)Telophase

  • PMAT







1. chromosomes visible (sister chromatids)

2. centrioles migrate to the poles (only in animals)

3. nuclear membrane disappears

4. spindle forms


1. chromosomes uncoil • now chromatin

2. nuclear membranes reform

3. spindle disappears

  • Occurs at end of Mitosis

    --division of the cytoplasm to form 2 new daughter cells

    --organelles are divided

    -Daughter cells are genetically identical

Cells return to interphase


  • Name the phases starting at the top.

2.Name the phase

3.Identify X

4.Identify Y

5. Name the phase

6. Name the phase

Control of the cell cycle
Control of the Cell Cycle

  • Regulatory proteins called cyclins control the cell cycle at checkpoints:

  • G1 Checkpoint—decides whether or not cell will divide

  • S Checkpoint—determines if DNA has been properly replicated

  • Mitotic Spindle Checkpoint—ensures chromosomes are aligned at mitotic plate

Cancer cells

  • Result of uncontrolled cell division of cells that have lost ability to regulate cell cycle

  • Reproduce more rapidly than normal cells

  • Masses formed called ‘tumors’

Lesson summary cell cycle
Lesson Summary—Cell Cycle

  • The cell cycle is a repeating series of events, characterizing the life of a eukaryotic cell.

  • Binary fission is a form of cell division in prokaryotic organisms that produces identical


  • As a eukaryotic cell prepares to divide, the DNA and associated proteins coil into a

    structure, known as a chromosome.

  • The DNA copies during the S phase of the cell cycle, resulting in a chromosome that

    consists of two identical chromatids, known as sister chromatids, attached at a region

    called the centromere.

  • Any cell containing two sets of chromosomes is said to be diploid; the zygote forms

    from the fusion of two haploid gametes.

  • The cell cycle has five phases: the first growth (G1) phase, the synthesis (S) phase,

    the second growth (G2) phase, mitosis, and cytokinesis.

  • Mitosis is the division of the nucleus; four distinct phases of mitosis have been

    recognized: prophase, metaphase, anaphase, and telophase.

  • Cytokinesis is the division of the cytoplasm.

  • The cell cycle is controlled through feedback mechanisms.

  • Cancer results from uncontrolled cell division, due to the loss of regulation of the cell